Appsflyer's Push API v2 recently integrate the new SKAdNetwork attribution.
After testing on current version (January 2021) of Fivetran Appsflyer connect, it seems this feature is not yet implement.
It would be nice if your team will look into it in the near future, as SKAdNetwork is the de facto and only standard for iOS 14.5+, no other data can be collect.
For your information, currently over 80% of iOS device has been updated to 14, and iOS 15 will be released soon. The impact is big.